Various front forks serving as hydraulic shock absorbers that are mounted on a front wheel side of a two-wheel vehicle so as to absorb a road surface impact input into the front wheel of the two-wheel vehicle while suspended across the front wheel have been proposed in the prior art. For example, JP4-8934A discloses a front fork that can increase or reduce a vehicle height of a two-wheel vehicle by adjusting a spring force of a suspension spring housed in a fork main body.
The front fork disclosed in JP4-8934A includes a plunger serving as a piston. The plunger is provided in series with a suspension spring housed in a fork main body constituted by a vehicle body side tube and a vehicle wheel side tube so as to contact an upper end of the suspension spring.
In this front fork, the plunger slides in an axial direction of the suspension spring in accordance with a supply and a discharge of pressure oil from the exterior of the fork main body, thereby raising and lowering an upper end position of the suspension spring such that the spring force of the suspension spring is adjusted.
At this time, the plunger is housed slidably within a cylinder disposed in an axial center portion on an upper end portion side of the vehicle body side tube. A lower end projecting from the cylinder is latched to an upper end of a tubular spacer. A lower end of the spacer is held on the upper end of the suspension spring.
Hence, in the front fork disclosed in JP4-8934A, the plunger is caused to slide by driving a pressure oil supply/discharge source provided in the vehicle body, for example, and thus the plunger adjusts the spring force of the suspension spring by raising and lowering the upper end position of the suspension spring. In other words, the front fork is capable of adjusting the vehicle height of the two-wheel vehicle.